Rohde & Schwarz 1164.4391.03, Руководство по обслуживанию

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Instrument Design and Function Description R&S FSP
1164.4556.82 3.2 E-1
Description of Block Diagram
The R&S FSP is a triple-conversion superjet receiver (double-conversion for receive frequencies
>3 GHz) for the frequency range from 9 kHz to several GHz, depending on the instrument model. The
signals are processed by one RF board (two for models > 3 GHz), one IF board, one signal detection
board and a controller comprising a Pentium-driven commercially available PC, an I/O interface and a
graphics controller. The instrument can be upgraded to meet future requirements by retrofitting options
in the analog and digital sections.
The input signal is reduced in level by the attenuator and routed to the RF modules depending on the
instrument type. In instruments with option R&S FSP-B25 (electronic attenuator), this module follows in
the signal path. In 3 GHz models, it directly follows the RF frontend; in the high-frequency models, a
diplexer is connected in between. The high-frequency signal component >3 GHz is routed to the
microwave converter module following the diplexer. The IF module is the same in all instrument models,
and likewise for the signal path through signal detection to the display.
The internal reference and calibration signals are generated in the frequency and level reference part on
the IF filter board. Here the 128 MHz reference frequency from the frontend is amplified and made
available to the instrument as a reference frequency, and a level-controlled output signal is generated as
an internal level reference for instrument calibration.
The tracking generator produces an output signal at the receive frequency with a frequency offset of
±150 MHz. The output level of the module is regulated and can be set in the range -30 dBm to 0 dBm.
The output signal can be externally I/Q-, AM- and FM-modulated.
A detailed description of the modules is provided in the following.
Attenuator
The RF signal passes from the input connector via the input switch to the input attenuator, which can be
set from 0 to 70 dB in steps of 10 dB. The input signal is applied to the switch as well as a 128 MHz
signal which has a close tolerance level of -30 dBm for calibration purposes or 0 dBm for the selftest of
the instrument.
Electronic Attenuator (Option R&S FSP-B25)
The electronic attenuator is fitted in the RF signal path directly behind the input attenuator. It consists of
three different parts: an 5 dB attenuator, which changes the input attenuation to 5 dB steps; an
electronic attenuator, which can be switched from 0 to 30 dB in steps of 5 dB; and a switchable
preamplifier to reduce the noise figure of the instrument.